Jack Cust hits a grand slam in the fourth inning to give the A's a 4-0 lead.

Photo: Brant Ward, The Chronicle

Jack Cust hits a grand slam in the fourth inning to give the A's a...

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Jack Cust is greeted in the dugout after his grand slam in the fourth inning including manager Bob Geren (right). The A's defeat the Rangers 9-4. The Oakland Athletics vs. the Texas Rangers at the Oakland Coliseum Thursday May 7, 2009.

Jack Cust became the second A's free agent to return to the fold, signing a $2.65 million, one-year deal with the team Thursday.

Cust, who is expected to primarily fill the role of designated hitter now that Oakland has another fulltime outfielder in Coco Crisp, can earn an additional $350,000 in incentives, based on plate appearances.

Oakland had not offered Cust arbitration, but A's assistant general manager David Forst said, "We said all along that was not an indication of our desire to bring Jack back or not. We felt it was the right move from a resource standpoint."

Forst said the A's hope had been to "get the last crack at it" and top any other offers Cust received, but it never came to that. The A's made an outright proposal Wednesday that Cust accepted Thursday morning.

The A's agreed to terms with Cust - who hit 25 home runs last year and has led the team in homers each of the past three seasons - the same day that third baseman Adrian Beltre, an Oakland target, officially became a member of the Red Sox. The A's were competitive in their bid for Beltre, according to a major-league source, including offering the infielder more guaranteed years (three years at about $25 million, or two at roughly $18 million).

Beltre signed a one-year deal with an option that will pay him a minimum of $10 million, according to reports.

The pursuit of Beltre indicates that Oakland is still hoping to land a third baseman or a shortstop who also can play third. So, might onetime A's infielder Miguel Tejada wind up in the picture? Oakland has contacted his agent, and if Tejada came at a bargain rate, as Orlando Cabrera did last year, there is a possibility that something could work out.

The A's still like another of their own free agents, Adam Kennedy, but the fact that he cannot play shortstop lessens the chances that he'll be back.

Oakland's own third baseman, Eric Chavez, is recovering from his second back surgery in two years, but he said Thursday that he already is throwing and he has fielded some groundballs.

"I've started to steamroll toward 100 percent," Chavez said.

Chavez is cautiously optimistic about his ability to return to third on at least a semi-regular basis. If he cannot, he and Cust probably would wind up sharing time at DH and both are left-handed hitters, not an ideal platoon situation.